PLANET EARTH Shallow Seas
At night, the algae are inactive but then, the polyps put out even more tentacles so coral in effect feeds around the clock. This well balanced alliance（同盟） brings benefits to both polyps and algae and between them, they turn the barren seas into rich gardens. The Indonesian reefs contain such a variety of life because they lie at a giant crossroads.
This is the meeting place for different seas the Indian Ocean and the Pacific. Here everything demands a closer look. On the surface of this sea fan, there are two polyps that are not polyps. They're pygmy sea horses（侏儒海马）, the world's smallest, less than two centimeters high. They are males, settling a territorial dispute, by head butting（用头撞）. An electric flash? No, the display of a file clam.
Perhaps this extraordinary pulsation of the clam's（蚌） fleshy mantle is a warning to frighten away nibbling（啃食） fish, but no one really knows, and there are snakes here, too, lots of them. These are banded sea crates. They lay their eggs on land but they hunt here in the water. They're too slow to catch fish in a straight chase so they seek prey that is hiding in the nooks（角落） and crannies（裂缝） of the coral. Their bite is highly venomous and paralyzes（麻痹） their victims.
